When you write a business application for some other organization or department, you might not care all that much about the security and integrity of the data managed by the software tool. As long as the data gets from the user's fingertips to the database and back, it's all hunky-dory.
Although such views may work for many applications, there are systems and users that expect much more in the way of security. Sometimes, you need to ensure the security and integrity of the data managed by the application, especially if it will leave the confines of your software or associated database. The security features found in the System.Security.Cryptography namespace provide a fun variety of data hiding and restoration options.